WO2022205647A1

WO2022205647A1 - Inductor and tunable filter

Info

Publication number: WO2022205647A1
Application number: PCT/CN2021/103437
Authority: WO
Inventors: 邱文才; 赵纶; 田学红; 林满院
Original assignee: 广东大普通信技术有限公司
Priority date: 2021-03-29
Filing date: 2021-06-30
Publication date: 2022-10-06
Also published as: CN113014221A

Abstract

Disclosed in the present application are an inductor and a tunable filter. The inductor comprises: a micro-electro-mechanical system (MEMS) multi-contact switch and a coplanar waveguide transmission structure. The coplanar waveguide transmission structure comprises a central signal line, and a plurality of support arms which are arranged on two sides of the central signal line; in a direction extending along the central signal line, at least one pair of support arms are arranged on at least two straight lines; and when the MEMS multi-contact switch is turned on, the central signal line is connected to a pair of support arms via the MEMS multi-contact switch.

Description

Inductors and Tunable Filters

This application claims the priority of the Chinese patent application with application number 202110335564.0 filed with the China Patent Office on March 29, 2021, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the field of wireless communication technologies, for example, to an inductor and a tunable filter.

Background technique

High-performance micro-filters can play important roles in multi-band wireless communication systems and wireless transceivers, such as channel selection, dual-power and image-removing spurious filtering. However, since the single-frequency filter used in the multi-band receiver cannot meet the needs of selecting multiple frequency bands at the same time, multiple single-frequency filters are usually added in the multi-band receiver to sort different frequency bands, thus increasing the multi-band frequency. Design dimensions of filter circuits in wireless communication systems for receivers.

In recent years, with the development of multi-frequency wireless communication systems in microwave and millimeter wave bands, tunable filters based on Micro-Electro-Mechanical System (MEMS) technology have gradually attracted widespread attention. The filter is composed of a variable reactance element, and the variable reactance element adopts a MEMS varistor as a tuning element, and the tunable range is 10%-15%. However, for discrete frequencies with wider tuning ranges, capacitive MEMS switches are often employed to achieve higher tuning ranges. In addition, another filter that achieves wide-range discrete frequency tuning is the use of quasi-fractal structure and MEMS contact switch. Since the inductive element of the filter adopts a distributed circuit design, the stop-band suppression of the filter is further improved. functionality is affected.

The design principle of the filter is to move up or down the frequency response of the filter by adjusting the values of the inductor L and the capacitor C. Therefore, the ideal tunable filter design requires not only variable capacitors, but also variable inductors. However, due to the non-planarity of the transition of the variable capacitor, the variable capacitor cannot be integrated with other circuits and cannot meet the requirements of the millimeter-wave filter for a small-sized planar structure.

SUMMARY OF THE INVENTION

The present application provides an inductor and a tunable filter, which are used to solve the defect of large circuit size when the inductor and capacitor form a filter, so that the filter can meet the requirements of the millimeter wave filter for the inductor of a small-sized planar structure.

Provided is an inductor comprising a MEMS multi-contact switch and a coplanar waveguide transmission structure;

The coplanar waveguide transmission structure includes a central signal line and a plurality of support arms arranged on both sides of the central signal line; along the extending direction of the central signal line, at least a pair of support arms are arranged on at least two straight lines; when the MEMS multi-contact switch is closed , the center signal line and the arms in a pair are connected through a MEMS multi-contact switch.

A tunable filter is also provided, including an inductor and a MEMS capacitive switch implementing any of the above;

Inductive and MEMS capacitive switch connections.

Description of drawings

FIG. 1 is a schematic structural diagram of an inductor provided by an embodiment of the present application;

2 is a schematic structural diagram of a MEMS multi-contact switch provided by an embodiment of the present application;

3 is a schematic structural diagram of another inductor provided by an embodiment of the present application;

4 is a schematic structural diagram of a tunable filter provided by an embodiment of the present application;

5 is a schematic structural diagram of another tunable filter provided by an embodiment of the present application;

6 is a schematic structural diagram of another tunable filter provided by an embodiment of the present application;

FIG. 7 is a schematic structural diagram of an equivalent circuit of a tunable filter provided by an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. The described embodiments are part of the embodiments of the present application, but not all of the embodiments.

An embodiment of the present application provides a schematic structural diagram of an inductor, and FIG. 1 is a structural schematic diagram of an inductor provided by an embodiment of the present application. As shown in FIG. 1 , the inductor includes a MEMS multi-contact switch 110 and a coplanar waveguide transmission structure 120 ; the coplanar waveguide transmission structure 120 includes a central signal line 121 and a plurality of arms 122 disposed on both sides of the central signal line 121 ; Along the extending direction X1 of the central signal line 121, at least a pair of support arms 122 are arranged on at least two straight lines; when the MEMS multi-contact switch 110 is closed, the central signal line 121 and a pair of support arms 122 pass through the MEMS multi-contact Switch 110 is connected.

Among them, the MEMS multi-contact switch 110 has the characteristics of being easy to use, small in size and low in loss, and can stably transmit signals from 0 to several hundreds of GHz. The coplanar waveguide transmission structure 120 has the characteristics of small size, light weight, and easy integration with other circuits. In one embodiment, the coplanar waveguide transmission structure 120 is composed of a central signal line 121 and a plurality of arms 122 disposed on both sides of the central signal line 121, and in the direction X1 extending along the central signal line 121, at least two straight lines are formed. At least one pair of support arms 122 are provided on the upper. Exemplarily, one side of the central signal line 121 is provided with a first support arm 123 and a second support arm 124, and the other side of the central signal line 121 is provided with a third support arm 125 and a fourth support arm 126; The extension direction X1 of the line 121, the first support arm 123 and the second support arm 124 are located on a straight line, the third support arm 125 and the fourth support arm 126 are located on a straight line; the first support arm 123 is away from the second support arm 124 One end of the second arm 124 is connected to the center signal line 121, one end of the second arm 124 away from the first arm 123 is connected to the center signal line 121, one end of the third arm 125 away from the fourth arm 126 is connected to the center signal line 121, One end of the four arms 126 away from the third arm 125 is connected to the central signal line 121 . In addition, the coplanar waveguide transmission structure 120 further includes a ground wire 127 . In the present application, by integrating the MEMS multi-contact switch 110 with the coplanar waveguide transmission structure 120 , when the MEMS multi-contact switch 110 is closed, the MEMS multi-contact switch 110 will bend downward to contact the center signal line 121 and a pair of supporting arms 122 , connecting the central signal line 121 with the supporting arms 122 in the pair, thereby changing the line connection of the coplanar waveguide transmission structure 120 , changing the inductance value of the coplanar waveguide transmission structure 120 , and realizing the independent change of the inductance value. Therefore, when the MEMS multi-contact switch 110 is closed, the MEMS multi-contact switch 110 is used to replace the switches between the arms 122 of the coplanar waveguide transmission structure 120, which reduces the total number of connected switches between the arms 122 and effectively reduces the The insertion loss reduces the overall size of the inductor and forms a small-sized planar structure inductor that meets the needs of millimeter-wave filters.

FIG. 2 is a schematic structural diagram of a MEMS multi-contact switch provided by an embodiment of the application. As shown in FIG. 2 , optionally, the MEMS multi-contact switch 110 includes a contact sheet 111 , a first driving board 112 and a second driving board 113; the contact piece 111, the first driving board 112 and the second driving board 113 are all provided with holes arranged in an array; along the first direction X2, the contact piece 111 includes a first end and a second end, and the first driving board 112 and the second driving plate 113 are respectively disposed on both sides of the contact piece 111 and are connected with the first end and the second end respectively; the first driving plate 112 and the second driving plate 113 can move toward the contact piece 111 along the first direction X2 ; wherein, the first direction X2 is the row direction of the holes arranged in an array on the contact sheet 111 .

The MEMS multi-contact switch 110 includes a contact piece 111 , a first driving board 112 and a second driving board 113 . In one embodiment, the first direction X2 is set as the row direction of the holes arranged in the array on the contact piece 111 . , in the first direction X2, the two ends of the contact piece 111 are the first end and the second end respectively, and in this direction, the first drive plate 112 is located at the first end side of the contact piece 111, and the second drive plate 113 is located at the first end side of the contact piece 111. The second end side of the contact piece 111 , and the first drive plate 112 is connected to the first end of the contact piece 111 , and the second drive plate 113 is connected to the second end of the contact piece 111 . The first driving board 112 and the second driving board 113 can move toward the contact piece 111 along the first direction X2. When the first driving board 112 and the second driving board 113 approach the contact piece 111 along the first direction X2 at the same time, the contact piece 111 will be subjected to the pressing force given by the first driving board 112 connected to the first end and the second driving board 113 connected to the second end at the same time, and then the contact piece 111, the first driving board 112 and the second driving board 113 At this moment, different degrees of mechanical deformation will occur. Since the contact piece 111 , the first driving board 112 and the second driving board 113 are all provided with holes arranged in an array, the flexibility of the contact piece 111 , the first driving board 112 and the second driving board 113 can be increased, preventing the contact piece 111 , the first driving plate 112 and the second driving plate 113 are damaged due to mechanical deformation during the pressing movement. In addition, when the MEMS multi-contact switch 110 is closed, the first driving board 112 and the second driving board 113 approach the contact piece 111 along the first direction X2 at the same time, and the first driving board 112 and the contact piece 111 are connected at the first end. When the second driving board 113 connected to the second end is squeezed at the same time, it will bend in the direction close to the coplanar waveguide transmission structure 120, so that the contact piece 111 contacts the center signal line 121 and the pair of supporting arms 122, and then the center signal The wire 121 and the arms 122 in a pair are connected through the contact piece 111 . Since the contact piece 111 has holes arranged in an array, a plurality of switches can be formed, thereby increasing the number of connection paths for the contact piece 111 to connect the central signal line 121 and the support arms 122 in a pair, that is, the contact piece 111 replaces many switches. The switches between the arms 122 can effectively reduce the insertion loss of the device, so that the overall size of the inductor can be reduced.

2, the MEMS multi-contact switch 110 further includes a first support beam 114 and a second support beam 115; along the second direction Y, the contact piece 111 includes a third end and a fourth end, the first support The beam 114 and the second support beam 115 are respectively disposed on both sides of the contact piece 111 ; the first end of the first support beam 114 and the first end of the second support beam 115 are respectively connected with the first drive plate 112 , and the first support beam The second end of 114 and the second end of the second support beam 115 are respectively connected to the second driving board 113 ; wherein, the second direction Y is the column direction of the holes arranged in an array on the contact sheet 111 .

The MEMS multi-contact switch 110 further includes a first support beam 114 and a second support beam 115 . In one embodiment, the second direction Y is set as the column direction of the holes arranged in the array on the contact sheet 111, and the two ends of the contact sheet 111 in the second direction Y are the third end and the fourth end respectively, and in the second direction Y In this direction, the first support beam 114 is located on the third end side of the contact piece 111 , the second support beam 115 is located on the fourth end side of the contact piece 111 , and the first end of the first support beam 114 and the second support beam 115 The first end of the first support beam 114 and the second end of the second support beam 115 are respectively connected with the second drive plate 113, and then the first support beam 114 and the second The support beam 115 can better provide support for the first driving board 112 and the second driving board 113, preventing the first driving board 112 and the second driving board 113 from moving too far along the first direction X2 to the contact piece 111 at the same time. , causing the contact piece 111 , the first driving plate 112 and the second driving plate 113 to deform too much and break during the extrusion movement.

FIG. 3 is a schematic structural diagram of another inductor provided by an embodiment of the present application. As shown in FIG. 3 , the inductor further includes a substrate 130 ; the coplanar waveguide transmission structure 120 is disposed on the substrate 130 , and the MEMS multi-contact switch 110 is disposed On the side of the coplanar waveguide transmission structure 120 away from the substrate 130 ; along the thickness direction of the substrate 130 , the orthographic projection 140 of the contact piece 111 partially overlaps the central signal line 121 and the arm 122 of the coplanar waveguide transmission structure 120 .

The substrate 130 may be quartz with a thickness of 520 microns, the coplanar waveguide transmission structure 120 may be a metal layer with a thickness of 3 microns, the coplanar waveguide transmission structure 120 is disposed on the substrate 130, and the MEMS multi-contact switch 110 is disposed in a common A side of the surface waveguide transmission structure 120 away from the substrate 130 . Along the thickness direction of the substrate 130 , the orthographic projection 140 of the contact piece 111 of the MEMS multi-contact switch 110 partially overlaps with the central signal line 121 and the support arm 122 of the coplanar waveguide transmission structure 120 , it can be seen that the area of the contact piece 111 is larger than If the first driving plate 112 and the second driving plate 113 approach the contact piece 111 along the first direction X2 at the same time, the contact piece 111 will be squeezed to the side close to the substrate 130 to form a convex shape. Then, the protruding part of the contact piece 111 can be in contact with the central signal line 121 and the pair of support arms 122, and the connection relationship of the coplanar waveguide transmission structure 120 is reconstructed, thereby changing the inductance value of the inductance.

In one embodiment, continuing to refer to FIG. 3 , the distance between the supporting arms 122 in the pair is smaller than the length of the contact piece 111 along the first direction X2 .

Exemplarily, the distance between the arms 122 in a pair of the coplanar waveguide transmission structure 120 is smaller than the length of the contact piece 111 along the first direction X2, the distance between the arms 122 in the pair is 20 microns, and the contact piece 111 The length along the first direction X2 is 100 microns. When the first driving board 112 and the second driving board 113 approach the contact piece 111 along the first direction X2 at the same time, the contact piece 111 will be affected by the first driving board 112 connected at the first end and the second driving board connected at the second end The contact piece 111 will protrude toward the direction close to the substrate 130 , so that the contact piece 111 communicates with the pair of support arms 122 . It can be seen that the distance between the support arms 122 in a pair is smaller than the length of the contact piece 111 along the first direction X2, so that the contact piece 111 can be connected to the pair of support arms 122 after the convex deformation.

In addition, the following table shows the dimensions of the coplanar waveguide transmission structure 120 in FIG. 3 .

参数parameter	W1W1	W2W2	GG	SS	L1L1	L2L2	L3L3
尺寸umsizeum	2020	3030	2020	4040	2020	220220	2020

FIG. 4 is a schematic structural diagram of a tunable filter provided by an embodiment of the present application. As shown in FIG. 4 , the tunable filter includes an inductor 100 and a MEMS capacitive switch 200 that implement any one of the foregoing embodiments; The inductor 100 is connected to the MEMS capacitive switch 200 .

The inductor 100 includes the inductor 100 provided in any embodiment of the present application, and thus has the effect of the inductor 100 provided by the embodiment of the present application, and details are not described herein again. In addition, the inductor 100 is connected to the MEMS capacitive switch 200. In the present application, by operating the inductor 100 and the MEMS capacitive switch 200, the inductance value of the inductor 100 and the capacitive value of the MEMS capacitive switch 200 can be independently changed, thereby making the passband characteristic of the tunable filter. The ideal Chebyshev prototype response characteristics are maintained.

FIG. 5 is a schematic structural diagram of another tunable filter provided by an embodiment of the present application. As shown in FIG. 5 , the tunable filter further includes a capacitor 300; the first end of the capacitor 300 is connected to the MEMS capacitive switch 200, and the capacitor 300 The second terminal is grounded.

Among them, the capacitor 300 has the characteristics of storing electricity, discharging and blocking direct traffic. By utilizing the power storage characteristic of the capacitor 300 , the first end of the capacitor 300 is connected to the MEMS capacitive switch 200 , and a bias voltage can be provided to the MEMS capacitive switch 200 . In addition, by using the characteristic of the capacitor 300 to block direct traffic, the first end of the capacitor 300 is connected to the MEMS capacitive switch 200, and the second end of the capacitor 300 is grounded, which can replace the bias decoupling circuit to introduce the noise generated in the filter circuit into the negative Extreme or ground terminal, and then realize the removal of noise generated in the filter circuit.

FIG. 6 is a schematic structural diagram of another tunable filter provided by an embodiment of the present application. As shown in FIG. 6 , the tunable filter includes an input end A, an output end B, two inductors 100 and three MEMS capacitive switches 200 ; Two inductors 100 are connected in series between the input terminal A and the output terminal B, and the three MEMS capacitive switches 200 are respectively connected to the input terminal A, the output terminal B and the connection point of the two inductors 100 .

Exemplarily, FIG. 7 is a schematic structural diagram of an equivalent circuit of a tunable filter provided by an embodiment of the present application. As shown in FIG. 7 , two inductors L are connected in series between the input end A and the output end B, and the MEMS capacitor is connected in series. The switch C ₁ is connected to the input terminal A, the MEMS capacitive switch C ₂ is connected to the connection point of the two inductors L, and the MEMS capacitive switch C ₁ is connected to the output terminal B. Among them, when the two inductors L are in the "down" state (that is, the closed state), and the MEMS capacitive switch C ₁ and the MEMS capacitive switch C ₂ are in the "up" state (that is, the open state), the tunable filter is in a "broadband" state. "state, the bandwidth is 57GHz at the moment. When the two inductors L are in the "up" state (ie, the open state), and the MEMS capacitive switch C ₁ and MEMS capacitive switch C ₂ are in the "down" state (ie, the closed state), the tunable filter is in the "narrow band" state , the bandwidth is 19GHz at the moment.

When the inductor is in the "down" state (ie, the closed state): the first driving board 112 and the second driving board 113 approach the contact piece 111 along the first direction X2 at the same time, and the contact piece 111 is connected at the first end of the first drive When the board 112 and the second driving board 113 connected to the second end are squeezed at the same time, the board 112 will bend in the direction close to the coplanar waveguide transmission structure 120, so that the contact piece 111 contacts the center signal line 121 and the pair of supporting arms 122. Furthermore, the central signal line 121 and the pair of supporting arms 122 are connected through the contact piece 111 .

The following table shows the estimated values of the inductance L, MEMS capacitive switch C ₁ and MEMS capacitive switch C ₂ in each state of the tunable filter, and the filtering bandwidth of the tunable filter in each state. It can be seen from the table that there is a deviation between the estimated values of the inductance L, MEMS capacitive switch C ₁ and MEMS capacitive switch C ₂ in the design and testing, which is caused by the slight downward deflection of the bridge of the MEMS, which makes the extracted inductance value within It has a parasitic series resistance of 2.3 ohms in the "broadband" state and 3 ohms in the "narrowband" state.

The tunable filter may further include a radio frequency choke coil, the first end of the radio frequency choke coil is connected to the input end A of the tunable filter, and the second end of the radio frequency choke coil is grounded. Wherein, the radio frequency choke coil is used to eliminate the coupling component in the input signal provided by the input terminal A.

Optionally, the MEMS switch capacitor includes an adjustable membrane bridge capacitor.

A gap will be formed between the insulating layer of the adjustable membrane bridge capacitor and the metal membrane bridge. When the voltage is applied, due to the existence of different charges in the metal bridge and the center wire, electrostatic attraction is generated, which makes the metal membrane bridge move downward, and the insulation Layers fit snugly. The insulating layer can not only prevent DC short circuit, but also can be used as a dielectric layer to form a metal injection molding (MIM) capacitor with the upper and lower metal plates. When the applied voltage is removed, the metal film bridge returns to its original state. The adjustable membrane bridge capacitor can change the capacitance value of the adjustable membrane bridge capacitor through the up and down movement of the metal membrane bridge, thereby realizing the independent change of the adjustable filter capacitance value.

Claims

An inductor, comprising: a microelectromechanical system MEMS multi-contact switch and a coplanar waveguide transmission structure;

The coplanar waveguide transmission structure includes a center signal line and a plurality of support arms arranged on both sides of the center signal line; along the extending direction of the center signal line, at least one pair of support arms are arranged on at least two straight lines; When the MEMS multi-contact switch is closed, the central signal line and the support arms in a pair are connected through the MEMS multi-contact switch.
The inductor according to claim 1, wherein the MEMS multi-contact switch comprises: a contact piece, a first driving board and a second driving board;

The contact piece, the first driving board and the second driving board are all provided with holes arranged in an array; along the first direction, the contact piece includes a first end and a second end, the first driving The board and the second driving board are respectively arranged on both sides of the contact piece, and are respectively connected with the first end and the second end; the first driving board and the second driving board can be along the the first direction moves toward the contact piece;

Wherein, the first direction is the row direction of the holes arranged in the array on the contact sheet.
The inductor of claim 2, wherein the MEMS multi-contact switch further comprises: a first support beam and a second support beam;

Along the second direction, the contact piece further includes a third end and a fourth end, the first support beam and the second support beam are respectively arranged on both sides of the contact piece; The first end and the first end of the second support beam are respectively connected with the first driving plate, and the second end of the first support beam and the second end of the second support beam are respectively connected with the first drive plate. The two driving boards are connected; wherein, the second direction is the column direction of the holes arranged in the array on the contact sheet.
The inductor according to claim 1, wherein one side of the central signal line is provided with a first arm and a second arm, and the other side of the central signal line is provided with a third arm and a fourth arm arm;

Along the extension direction of the central signal line, the first support arm and the second support arm are located on a straight line, and the third support arm and the fourth support arm are located on a straight line; the first support arm and the fourth support arm are located on a straight line; One end of the arm away from the second arm is connected to the central signal line, one end of the second arm away from the first arm is connected to the central signal line, and the third arm is away from the center signal line. One end of the fourth support arm is connected to the center signal line, and one end of the fourth support arm away from the third support arm is connected to the center signal line.
The inductor of claim 2, further comprising: a substrate;

The coplanar waveguide transmission structure is arranged on the substrate, and the MEMS multi-contact switch is arranged on the side of the coplanar waveguide transmission structure away from the substrate; along the thickness direction of the substrate, the The orthographic projection of the contact piece overlaps with the central signal line and the arm portion of the coplanar waveguide transmission structure.
The inductor of claim 2, wherein the spacing between the arms of the pair is less than the length of the contact piece in the first direction.
A tunable filter, comprising: the inductance and MEMS capacitive switch of any one of claims 1-6;

The inductor is connected to the MEMS capacitive switch.
The tunable filter of claim 7, further comprising: a capacitor;

A first end of the capacitor is connected to the MEMS capacitive switch, and a second end of the capacitor is grounded.
The tunable filter according to any one of claims 7-8, the tunable filter comprising: an input end, an output end, two inductors and three MEMS capacitive switches;

The two inductors are connected in series between the input terminal and the output terminal, and the three MEMS capacitive switches are respectively connected to the input terminal, the output terminal and the connection point between the two inductors.
8. The tunable filter of claim 7, wherein the MEMS switched capacitor comprises a tunable membrane bridge capacitor.